It is extremely difficult to master the art of archery as many variables affect the accurate delivery of an arrow to a desired target. One of the most difficult variables is an accurate estimation of the distance from the archer to the intended target (the “target distance”). An arrow falls to earth at an accelerating rate on its way to the target due to the effects of gravity. This is the nature of the trajectory of any projectile. The archer requires extreme accuracy in range estimation in order to effectively place an arrow at a desired target. The use of an aiming point (e.g., at least one sight pin) in conjunction with a peep sight (e.g., an eyelet hole) on the string of a bow can provide this accuracy if the exact distance to the target can be ascertained. However, a separate sight pin or adjustable sight pin is then additionally required for each incremental target distance. FIG. 1 schematically illustrates this concept. The eye 10 of the archer (not shown) is aligned with an aiming point pin 13 located at the bow 15 to form a sight axis 17 that linearly extends through an intended target 20. The arrow 19 must be launched by tilting the bow 15 upward at a slight angle of a few degrees, as shown, in order to overcome gravitational acceleration. This defined curve 21, representative of the flight path of the arrow 19, passes through the sight axis 17 at two points, a first point 25 in a proximate area in which the arrow 19 is initially launched and a second point 27 on the way down. The effective target distance is typically mapped at the second point 27 on the way down where the arrow 19 intersects the sight axis 17 at the intended target 20. This is the distance that the archer is interested in hitting the target 20 with the arrow 19. With a traditional single aiming point sight device and as shown in FIG. 1, the effective accuracy of the bow 15, shown schematically by the boxes labeled with reference numerals 29, 31, is good for only a few yards in front and behind the target 20, respectively.
To that end, numerous drawbacks exist in the reliability and effective use of prior art sighting devices for archery bows as well as other launching devices in which a projectile is directed (i.e., launched) at a target and is influenced by gravity. Various target distance aiming devices (i.e., rangefinders) have been devised, including some that employ mirrors. All of these devices, however, are configured to require the user, such as a bow hunter, to make some sort of real time adjustment during the act of aiming in addition to judging the target distance.
In the field of archery, various bow sights have been shown for increasing the archer's accuracy, but these sights have acted merely as rangefinders. For example, U.S. Pat. No. 2,001,470 describe a folding bow having a top and bottom mirror acting as a periscope to reflect an image of the target to the eye of the archer. The lower mirror is rotationally articulated to align cross hairs on the lower mirror with the target. The lower mirror must be rotated to pre-arranged positions, which relate to various distances which the archer must estimate by other methods.
U.S. Pat. No. 3,163,697 shows a dual spaced mirror device arranged such that the viewer (archer) will simultaneously see both a real and a reflected target image. As a viewer looks at the target, a slide is manipulated until real and reflected images are both seen at the same height. At this position, the bow is aimed at the target and is properly positioned such that an arrow will assume the proper trajectory to the target.
U.S. Pat. No. 3,524,440 describes a mirror sighting device with respectively arranged upper and lower mirrors with cross hairs being added onto one of the mirrors. The lower mirror of this device is focused on the target while the upper mirror is focused on the lower mirror and reflects the target image to the archer's eye. The mirror mounting the cross hairs may be adjusted vertically in order to compensate for distance to the target.
U.S. Pat. No. 2,788,701 describes a device which incorporates multiple mirrors that are mounted below a single upper mirror for reflecting the image of the target and transmitting the image to the eye at various levels to facilitate trajectory adjustment of the bow for delivery of an arrow to the target.
U.S. Pat. No. 4,178,693 relates to an archery bow sight and range finder, including a pair of vertically spaced and laterally extending mirrors slidably mounted on a bow attached bracket and finger trigger which is actuable by the archer when grasping and aiming the bow. A center bead is associated with the lowermost mirror and the angle of the upper mirror is changed by trigger action to vary the elevation angle of the bow, with split image viewing being employed, combined with trigger action, to locate the exact range of target, one half of the target being viewed directly and the remaining half being seen through the mirrors. A lateral point of aim is determined by the lower mirror bead being positioned in the center of the combined split image.
U.S. Pat. No. 4,507,874 describes a bow sight which is characterized by a periscope device enclosing a top mirror and a bottom mirror to direct an image of a target to the eye of the archer. A compensating mirror is also mounted in the periscope in parallel adjustable relationship with respect to the top and bottom mirrors. A split target image is viewed in the fixed bottom mirror and comparison of this split image facilitates raising the bow to a proper angle in order to compensate for the trajectory of an arrow.
U.S. Pat. No. 4,555,856 describes a bow sight which includes, a housing enclosing a bottom mirror, a top mirror mounted in spaced relationship in the housing with respect to the bottom mirror and a narrow compensating mirror positioned in the housing in close proximity to the bottom mirror. The top and bottom mirrors are mounted in substantially parallel relationship at approximately a 45 degree angle in the housing and the top mirror and the compensating mirror are pivotally mounted with the compensating mirror adjustably responsive to manipulation of a lever from a calibrated position. The target image segment projected from the top mirror to the bottom mirror is compared to the target image segment projected from the compensating mirror to the bottom mirror and the lever is moved in order to provide the necessary adjustment to align the segments and determine a proper trajectory for accurately delivering an arrow to the target.
U.S. Pat. No. 4,979,309 describes a range finding bow sight for archery bows which includes a frame on which are mounted upper and lower mirrors in a substantially parallel relationship at a 45 degree angle and vertically aligned with each other forwardly of the bow. The top mirror is pivotally mounted and adjustably responsive to manipulation of a lever, which cooperates through a programmed cam segment on a rotationally mounted sighting plate to which is attached a sight pin. Movement of the actuating lever correspondingly shifts the upper mirror to permit alignment of the actual target image with a reflected target image from the lower mirror. Movement of the actuating lever simultaneously positions the sight pin to provide the necessary elevation of the bow for the proper trajectory of the arrow to the target. The programmed cam section is removable and can be shaped to match the performance characteristics of the archery equipment being used.
None of the above-noted prior art, nor any that Applicants are presently aware, solve the general and persisting need in the archery industry, at a minimum, to provide a sight that is readily adaptable to long bows, recurve bows, compound bows, cross bows, and other projectile devices, which can accurately aim over various distances between the user and an intended target without the need to estimate or measure the target distance.